1. Field of the Invention
The invention relates to a liquid cell for fixing a sample when the sample is observed in a liquid solution by a scanning probe microscope.
2. Description of the Related Art
As widely known to the public, as a device for measuring a sample such as a metal, a semiconductor, a ceramic, resin, a polymer, a biomaterial, or an insulator in a microscopic region to perform measurement, observation, and so on of physicality information of the sample such as viscoelasticity thereof or the surface profile of the sample, a scanning probe microscope (SPM) is known. The scanning probe microscope offers various modes of measurement methods selectable in accordance the sample as the target of the measurement or the observation. An in-liquid measurement mode for observing the sample in a solution such as a culture solution is one of such measurement modes.
In the in-liquid measurement mode, the measurement is usually performed in the condition in which the cantilever and the sample are both completely dipped in the solution. In this case, there are various methods of fixing the sample. In a typical scanning probe microscope, there is adopted a method of fixing the sample to a dedicated stage so as to hold the sample down on the stage using a plurality of screws (see, for example, Patent Document 1). According to this method, since the sample can securely be fixed at a predetermined position, the in-liquid measurement can surely be performed.
Meanwhile, there are also provided various kinds of liquid cells used by only sinking the sample in the solution (see, for example, Patent Documents 2, 3).
[Patent Document 1] JP-A-9-89909
[Patent Document 2] JP-A-2003-121335
[Patent Document 3] JP-A-9-54098
Meanwhile, in the conventional method described above, the following problems were left unsolved.
Namely, in the sample fixing method utilizing a plurality of screws described in the Patent Document 1 and so on, it was necessary to adjust the tightening torque to be equal in each of the screws for fixing the sample on the level. However, the adjustment was difficult and required experience, and also required operation time even for a skilled operator. Further, since the sample is exposed to the atmosphere during the adjustment is performed, long operation time raises the probability of occurrence of the deterioration such as drying or oxidization. There were some cases in which a harmful influence was exerted to the measurement.
Further, it is necessary to perform the operation of attaching and detaching the plurality of screws every time the sample is fixed. There is a probability of contamination caused by the screw dropping off and touching the surface of the sample. There were some cases in which the measurement became difficult.
On the other hand, in the liquid cell used for only sinking the sample in the solution, the sample might float depending on the specific gravity. Therefore, there was a limitation that the sample with sufficiently greater specific gravity than the solution can only be used. It was not a method applicable to all of the samples.